Embodiments of this disclosure relates generally to extending a length of service of component parts, and more particularly, to method of extending a length of service of component parts so if a shape of the component changes during the process, the shape and size of the component still remains within a specified tolerance envelope to be used in final assembly.
In many aircraft, structural components may experience advanced dynamic changes. These advanced dynamic changes generally occur in features of the component such as in and around indentations, slots, holes, other types of openings, discontinuities or transition areas (hereinafter features). Advanced dynamic changes in these or other areas of the component may result in operating restrictions, and/or grounding of the aircraft.
Presently, there are several different methods to extend the length of service of structural components that may experience advanced dynamic changes. Coldworking is a process of expanding metal at a temperature below its annealing point in order to increase its hardness and tensile strength. Several methods of coldworking can be used. One method pushes a shaft having an enlarged diameter portion (commonly referred to as a mandrel) through an opening from one direction to radially expand the opening and compress the surrounding region to achieve a desired strain hardening. Another method involves lining the opening with a sleeve and pulling a mandrel through the sleeve to expand and thereby coldwork the opening. A further method includes inserting a collapsible mandrel (also known as a split mandrel) in collapsed form through the opening, expanding the mandrel, and then pulling the mandrel back through the opening to coldwork the opening. All of these methods require the feature to be present prior to coldworking. These methods may be difficult to automate.
Another method to extend the length of service of structural components that may experience advanced dynamic change is called StressWaving. StressWaving is a form of coldworking wherein compressive residual stresses are applied around areas of the component which may experience advanced dynamic changes. An indentation device is used to create the residual stresses around the areas of the component which may experience advanced dynamic changes. StressWave coldworking allows the coldworking process to be automated. Stresswaving imparts beneficial residual stress into a location prior to addition of a feature. The residual stresses applied increases the hardness and tensile strength of the area. After the StressWaving process, different features may be fabricated in to the component.
The coldworking process and adding the features may cause the component to change from its original shape and size. This is especially true when the component has a complex shape, a large number of areas of a component that need to be coldworked and/or when features formed in a component have a complex shape. Attempts to change the component back to its original shape and size may require the component going back through a stress relieve process that may eliminate the coldworked zone put into the component or may result in a non-beneficial high residual stress in the component.
Therefore, it would be desirable to provide a method of extending a length of service of component parts so that even if a shape of the component changes during the process, the size and shape of the component will remain within a specified tolerance envelope to be used in final assembly without high residual stress.